Despite numerous studies that have been carried out on plaque, saliva and tooth mineral, very little is known about events taking place in the model which permits the determination of many of the relevant physicochemical parameters on the ultramicro scale within "white spots" and sound enamel under a wide variety of conditions outside the tooth. Enamel sections 200 to 750 Mum thick are sealed on one side and cemented to a thin plastic sheet on the other. Microscopic wells, 50 to 100 Mum in diameter, are drilled through the plastic sheet into sound or caries regions in he enamel section, depending upon the nature of the experiment. Test solutions are deposited into these wells and the change in composition of these solutions is followed as functions of time and the composition of the external medium. The composition of the solution in the microwell is determined through the use of specific ion electrodes or through microcolorimetric analysis. Galvini potentials are simultaneously determined with microreference electrodes. The goals of this research are: (1) to obtain data defining the time scale of events occuring within the lesion during caries information; (2) to develop a valid mechanism of the caries process; (3) to obtain iformation about the physical properties of enamel relevantn to mineralization and demineralization; (4) to discover which part of the caries process is most amenable to interruption or reversal; and (5) to devise new micro and ultramicro techniques for the analysis of oral tissues.